1. Field of the Invention
The present invention relates to image projectors, more particularly, to an image projector that operates interchangeably between daytime vision scenarios and night time vision scenarios.
2. Description of the Prior Art
In order to simulate night time training using actual night vision devices such as goggles, monoculars, or scopes in a indoor firearms simulator, the displayed image that is seen by the naked eye must appear to be very dark, having hard-to-see details (just like at night), and the details of the displayed image must appear clear to the user when the user is looking though an actual night vision device.
The night vision device has an image intensifier that detects and amplifies a small amount of visible and infrared light. Traditionally, this has been accomplished by filtering the displayed image from the projector with an external filter (night vision filter) that only allows some visible and all the infrared light though to simulate night vision training. This filter is usually contained in a mechanical assembly that slides across the lens into the light path when night training is required (night vision mode), and then slides out of the light path when day training is required (normal mode).
The type of mounting described above requires an external mounting of the mechanical assembly to the projector. The mechanical assembly needs to be at least two times larger than the lens diameter of the projector in order to operate in the two modes of training and motorized for automatic operation. Consequently, this external mounting suffers from several problems. First, it is a cumbersome assembly that may be difficult to securely handle and provides a “clumsy” appearance of the projector to the user. Furthermore, the night vision mechanical assembly is easily damaged due to external mounting. In addition, this mechanical assembly is expensive to produce due to the various components required for operation, and it is additionally expensive to attach the present device to a particular projector. The introduction of a filter in the imaging part of a projector, between the light valves and the projection screen, will cause a degradation to the image quality, due to the change in optical distance, the possible presence of smudges or scratches, and the possibility to have double reflections in the image.